This invention relates generally to painting equipment for spray painting lines and traffic control indicia on pavement and more particularly relates to a glass bead dispensing apparatus for applying reflective glass beads onto a freshly painted line. The invention provides cost savings, improved convenience and enhanced operation of a walk behind, wheeled line striper, which is a machine in common use throughout the world. The invention also provides a glass bead dispensing apparatus that is easily demountable from the line striper for alternative use as a hand held bead dispenser.
Most painting contractors, who paint lines and traffic control indicia on pavement, use one of a few walk behind, wheeled line stripers purchased from two major manufacturers of these machines. An example is illustrated in FIG. 1 and some of its structural parts will be subsequently described in more detail. The wheeled line striper is a wheeled carriage which carries spray painting equipment including a paint sprayer, a paint supply tank, a high pressure paint pump suitable for applying a high pressure to the paint so that paint exits the sprayer under high pressure, an engine for powering the paint pump and interconnecting conduits for conveying paint. The carriage can be propelled by an on-board engine or pushed by a human operator or a separate ridden engine. A hand trigger is mounted to carriage handles at the rear of the carriage where the trigger is accessible to a human operator who is propelling the line striper during a line painting operation. The hand trigger is connected to the sprayer by a mechanical link, such as an actuation cable, for manually actuating the sprayer to paint a line as the line striper moves along the pavement
Although the sprayer can be fixed to the line striper, the sprayer of most line stripers is a demountable paint spray gun that is supported in a spray gun cradle. The line striper has a movable sprayer operator that moves the spray gun trigger to initiate spraying when the painter, who is walking or riding behind the line striper, actuates the hand trigger at the rear of the line striper. The cradle also allows the paint spray gun to be detached from the cradle so that the painter can use the spray gun to manually paint indicia other than stripes on the pavement. For example, a painting contract may include not only the painting of lines but may additionally include painting lane turning arrows, words or handicap parking symbols using stencils. The detachability of the paint spray gun allows the use of a single spray gun, which is conveniently available and easily accessible to the painter, for both manually painting such indicia and then returning the paint spray gun to the line striper to resume painting lines.
Many painting contracts require the application of glass beads to the paint in order to make the painted lines and traffic indicia reflect light from vehicles or other light sources. The beads must be applied while the paint surface is tacky or wet so they will adhere to the paint. In an attempt to provide this function for line painting, glass bead dispensers have been mounted to prior art line stripers aft of the paint sprayer. An example is shown in U.S. Pat. No. 6,478,507. [Because line stripers are vehicles that move across pavement when performing their painting operation, the terms front, back, rear, fore, forward and aft are used to describe relative positions and orientations and have meanings that are equivalent to the manner those words are applied to automobiles and boats]
In order to support both the paint sprayer and the glass bead dispenser on the line striper, line stripers have a horizontal support bar to which the paint spray gun cradle and the glass bead dispenser are mounted. This horizontal support bar extends in a fore/aft orientation, parallel to the line of travel of the striper. The sprayer is mounted forward of the bead dispenser so that glass beads from the dispenser can fall onto a freshly painted stripe as the line striper moves along the pavement. Ordinarily, the horizontal support bar can be raised and lowered in order to raise and lower the sprayer. Because the paint is sprayed from the sprayer nozzle in a diverging fan pattern, the width of the painted line can be increased and decreased by respectively raising and lowering the support bar and with it the sprayer.
Although the prior art line sprayers perform their intended function well, they also have some important deficiencies and problems which the present invention solves. Generally, the present invention provides enhanced cost benefits added convenience and avoidance of some operational and maintenance problems.
One deficiency of the prior art line stripers is that the glass bead dispenser is permanently mounted to the line striper. The result is that a painting contractor must either buy a second, hand-held bead dispenser or dispense glass beads onto freshly painted indicia from his or her hand or a hand held container. However, dispensing glass beads from the hand results in a bead distribution that is irregular and leaves areas of insufficient concentration and therefore less reflectivity. Casting glass beads onto the paint from the height of a human hand above the pavement permits a wind to carry many of the beads onto unpainted surfaces of the pavement. Those beads are wasted and cannot practically be retrieved.
Therefore, there is a need for a glass bead dispensing apparatus that can be quickly and easily demounted from the line striper, converted to a manual bead dispenser, used to apply glass beads to traffic indicia that were hand painted with a stencil and then quickly and easily returned to the line striper. The ease and timing for making these conversions are important because the painter wants to spend as little time as possible detaching, assembling or reattaching tools because doing so extends the time required for completing performance of the paint contract.
Another shortcoming of prior art line stripers is that their glass bead dispensers are not vertically adjustable independently of their sprayer. Although line stripers permit the horizontal support bar to be vertically adjusted to raise and lower the sprayer in order to widen or narrow the sprayed line, their bead dispenser, which is mounted to that horizontal support bar, is raised and lowered with the support bar. Consequently, when the horizontal support bar is raised, the bead dispenser is also raised to a greater height above the pavement. That greater height allows a wind to blow the dispensed beads farther from the painted line where they fall on unpainted surfaces of the pavement. This also leaves areas of insufficient bead concentration and less reflectivity Therefore, there is a need for a bead dispenser that can be raised and lowered independently of the horizontal support bar so that, when the support bar is raised, the bead dispenser can be lowered down to a more desirable lower height above the pavement where the dispensed beads are less susceptible to deflection by the wind.
Yet another problem with the prior art presents a dilemma to a designer who applies the prior art to the design of a line striper. Bead dispensers have a bead container with a horizontal exit slot near their bottom and a gate that pivots between a position blocking the exit slot and a position away from the exit slot to permit glass beads to pour out through the exit slot onto a freshly painted line. Some prior art line stripers have their bead dispenser oriented on the line striper with their gate on their upstream side of the dispenser facing forward toward the paint sprayer. Other line stripers have their bead dispenser oriented on the line striper with the gate on their downstream stream side facing aft away from the paint sprayer. However, each orientation presents a different problem but the invention solves both.
If a line striper of the prior art has its bead dispenser gate on the forward side of the bead dispenser so that it faces upstream toward the paint sprayer, suspended paint droplets that have not contacted the pavement are blown by a wind onto the bead dispenser. This overspray accumulates on the bead container of the dispenser and its gate, which is open during spraying. Particularly troublesome is the accumulation of paint on interfacing surfaces between the gate and the dispenser container in the area around the exit slot. Paint accumulated on these surfaces interferes with the dispenser's operation, for example by causing the gate to stick closed or causing any gasket material on the gate to stick to the bead container when the gate is closed and be torn away when it is opened.
Other line stripers of the prior art have their bead dispensers oriented in the opposite direction so their bead dispenser gate is on the aft side of the bead dispenser facing downstream away from the paint sprayer. In this aft-facing orientation, the bead container acts as a shield which avoids the above-described overspray problem but adds a new problem. If the pavement has an uneven surface such as hills, ledges or a protruding stone, the bottom of the gate can scrape or drag along the pavement. This frictional engagement with the pavement pulls the gate open. That is not a significant problem while spraying a line because whenever the painter, who is walking behind the striper, has actuated the trigger handle on the line striper, the bead dispenser is already opened. So paint is applied to the pavement and beads are applied onto the undried paint with little or no undesirable consequence.
However, scraping the gate along the pavement becomes a problem with a prior art line sprayer if the scraping happens when the line sprayer is being moved from the end of a line into position for painting the next line. It is obviously undesirable for paint to be sprayed onto an unintended area of the pavement while moving the line sprayer from one line to the next line. The painter must stop painting and clean that paint off the pavement. However, with prior art line sprayers, if the gate drags along the pavement and is pulled open while the line sprayer is moving between locations of desired paint applications, the movement of the gate to its open position also triggers the sprayer and causes paint to be sprayed. The result is that paint is sprayed onto the pavement at an unwanted location and continues to be sprayed until the gate rises above the pavement and closes. The reason for this unwanted spray is that the prior art has a fixed length, solid rigid rod that links the sprayer trigger to the bead dispenser gate for opening the gate when the sprayer is actuated. The problem with the prior art is that the trigger of the sprayer and the gate of the bead dispenser move in unison regardless of which is forced to its open position.
Therefore, there is a need for a bead dispenser apparatus that allows the bead dispenser gate to face downstream so it is shielded by the bead container but will not cause the paint sprayer to be accidentally actuated if the bead gate is inadvertently scraped open by a high spot on the pavement.
Another inadequacy of prior art line stripers is that the fore and aft distance of their bead dispenser from the sprayer cannot be adjusted or varied because their bead dispenser is fixed to the horizontal support bar. A painter may want to change the distance of the bead dispenser from the sprayer in order to apply the beads sooner after a paint with highly volatile solvent is applied to a hot pavement in order to control the paint drying time until the beads are applied to the paint. Also, the painter may want to move the bead dispenser farther from the sprayer on a windy day to minimize the overspray that blows onto the bead dispenser. Unfortunately, even if an owner of a line striper wished to vary that distance, the distance cannot be varied because of the rigid actuating link connected to the bead dispenser. Any fore and aft relocation of the prior art bead dispenser would result in the gate of the bead dispenser failing to open or would result in it being permanently held open at all times. Therefore, there is a need for a bead dispensing apparatus that permits the bead dispenser to be adjustably moved closer or farther from the sprayer.
Additionally, since the bead dispensing apparatus of the present invention is an after-market product that is installed on the line striper by the painter, there is a need for a bead dispenser that does not require that it be mounted at a critically precise location on the line striper's horizontal support bar but rather can be attached anywhere within a wide range of fore and aft locations.